1. Field of the Invention
The present invention relates to a choke transformer used in liquid crystal display (LCD) backlight driver. More particularly, the present invention relates to a choke transformer used in LCD backlight driver, in which a winding base is devised in structure so that an air gap is provided between the winding base and the core, through which the choke transformer may have a higher endurable voltage.
2. Description of the Prior Art
Referring now to FIG. 1, a cross sectional view of a transformer used in a conventional liquid crystal display (LCD) backlight driver is depicted therein. As shown, the transformer 1 is composed of a winding base 11, a core 12 and a plurality of windings 13. On the winding base 11, a plurality of spacers 111 are formed. Between two neighboring one of such spacers 111, a portion of the plurality of windings 13 of different characteristics are wound. In the winding base 11, there is a hollow structure within which the core 12 is centrally provided. At a conjunction where the winding base 11 and the core 12 joint, the winding base 11 and the core 12 may not achieve a total planar contact and thus between contact surfaces of the winding base 11 and the core 12 is a very small and non-uniform air gap. For an air gap of 0.003˜0.02 mm, only a voltage lower than 300V (measured in Vrms) may be endured, as shown in Table 1. When the supplied voltage becomes higher and higher, the windings may have charges discharged towards the core 12, leading to ionization of the air and thus arc light taken place. At this time, the transformer 1 fails to work in a normal manner.
TABLE 1Relationship between breakage voltage of air and distanceDistance (mm)Breakdown Voltage (Vrms)130000.520000.3515000.210000.023000.012500.003300
From the above description and Table 1, it can be readily known that such conventional transformer is inherent with some drawbacks and needs to be addressed and improved.
In view of these problems encountered in the prior art, the Inventors have paid many efforts in the related research and finally developed successfully a choke transformer used in LC backlight driver, which is taken as the present invention.